The present invention relates to a communication, and more particularly, to methods and apparatus for performing protocol data unit (PDU) header re-synchronization in a communication system.
FIG. 1 illustrates a frame structure typically utilized in a wireless communication system such as a Worldwide Interoperability Microwave Access (WiMAX) communication system according to the related art, where the WiMAX communication system may communicate by utilizing downlink (DL) bursts and uplink (UL) bursts according to the frame structure shown in FIG. 1. An example of a DL burst format for the frame structure shown in FIG. 1 is illustrated as shown in FIG. 2. In addition, examples of a medium access control (MAC) header of a MAC PDU typically utilized in the DL burst format shown in FIG. 2 are further illustrated as shown in FIG. 3.
According to the related art, when an error related to the MAC header shown in FIG. 3 occurs (for example, the MAC header shown in FIG. 3 is not decoded correctly), the length of the payload shown in FIG. 3 may be incorrect or unknown since the content in the field “LEN MSB(3)” and the content in the field “LEN LSB(8)” are not guaranteed in the situation where HT=0. As a result, it takes the WiMAX communication system more time to recover to normal operation; that is, to be in a synchronization state for deriving correct data carried by the DL bursts. More particularly, when it is designed to utilize the CRC32 information (which exists at the end of the MAC PDU, as shown in FIG. 3) in order to recover to the normal operation mentioned above, the WiMAX communication system typically needs to capture a whole MAC PDU. Thus, memory access corresponding to capturing a whole MAC PDU of a specific size (e.g. 2K bytes) into a data buffer is required whenever the same error occurs, even though the data temporarily captured within the data buffer may be not related to a connection under consideration.
In addition, the CRC32 information may be optional for some MAC PDUs. That is, if the WiMAX communication system waits for the appearance of the CRC32 information of another PDU derived in the future, some important data may be omitted before the WiMAX communication system recovers to the normal operation mentioned above. Therefore, the performance of the WiMAX communication system according to the related art is poor, since its operation is neither reliable nor time-efficient.